Delta Tau Universal PMAC Lite, Справочник по аппаратуре

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Universal PMAC Lite
PMAC-PC Software Setup 58
To make the change in CPU frequency and baud rate over the serial port with on-line commands, make
sure that the two commands are on the same command line. If they are on separate command lines, the
second command will not be accepted because the baud rate has changed. For example, with the same
setup as the above example, use the command line
M99=3 M98=2*M98+1
to change the CPU frequency and baud rate divider (to keep the baud rate constant) together.
Option 16 Supplemental Memory
If the Option 16 supplemental battery-backed parameter memory is ordered, an extra bank of memory
with battery backup circuitry is provided. This option can only be ordered if the main memory is flash
backed (Option 4A, 5A, 5B, or 5C). This memory is for user parameter storage only. From PMAC
programs, it can be accessed with M-variables only (L-variables also in compiled PLCs). The on-line
direct-memory read and write commands can be used from the host computer as well.
With M-variable access, arrays can be created with indirect addressing techniques by pointing a second
M-variable to the definition of a first M-variable that points into this memory area. For example, with the
M-variable definitions:
M0->L:$A000 ; 1st long word of Opt. 16 RAM; floating point
M10->Y:$BC000,0,16 ; Low 16 bits of M0 def., with pointer address
the following code segment could load a sine table into the first 360 words of the Option 16 RAM:
P1=0
WHILE (P1<360)
M10=$A000+P1
; Sets address that M0 points to
M0=SIN(P1) ; Puts value in register that M0 points to
P1=P1+1
ENDWHILE
Note that this technique is not possible with L-variables in compiled PLCs (but it is possible with M-
variables in compiled PLCs).
Physically, the Option 16 memory is a 16k x 24 bank of battery-backed static RAM. It maps into the
PMAC and PMAC2 at addresses $A000 to $BFFF, on both the X and Y data buses, an 8k x 48 block of
address space. Addresses Y:$BC00 to Y:$BFFF are double mapped with the main flash-backed RAM for
the M-variable definitions, and should not be used for user parameter storage.
Any value written into the Option 16 memory will be retained automatically through a power-down or
reset; no
SAVE
operation is required. Typically, the power draw on the battery is low enough that battery
life will be limited only by the quoted 10-year life of the battery.